


The Deep End of Our Little Ocean

by wallmakerrelict



Category: Voltron: Legendary Defender
Genre: M/M, MerMay, Merman Shiro, Non-Human Genitalia, Scientist Keith
Language: English
Status: Completed
Published: 2019-05-19
Updated: 2019-05-19
Packaged: 2020-03-08 01:42:40
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,380
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18885547
Author URL: https://archiveofourown.org/users/wallmakerrelict/pseuds/wallmakerrelict
Summary: “Is this okay?”Keith asks this a lot. He knows Shiro doesn’t understand him, but he asks anyway and Shiro seems to like it. Most creatures like to be talked to. Cryptids like Shiro and the others at the facility are no different. The words don’t matter. They respond to Keith's voice, his inflection, his body language. Even if they aren’t intelligent enough to understand what permission is, they trust Keith more for asking for it.In which Keith has a crush and Shiro understands better than he thinks.





	The Deep End of Our Little Ocean

**Author's Note:**

> Inspired by the incredibly beautiful and gloriously sexy mer-Shiro designed by @skyfangz on Twitter, in all his glory [here](https://twitter.com/daddy_skye/status/1127818599186305024) and [here](https://twitter.com/daddy_skye/status/1128597004555132928).

“Is this okay?”

Keith asks this a lot. He knows Shiro doesn’t understand him, but he asks anyway and Shiro seems to like it. Most creatures like to be talked to. Cryptids like Shiro and the others at the facility are no different. Not enough of the staff here seem to appreciate this, instead going about their duties as if they’re working with objects instead of living beings. Keith talks to them, all the time, with an ease he can’t seem to replicate when he tries to talk to humans. The words don’t matter. They respond to his voice, his inflection, his body language. Even if they aren’t intelligent enough to understand what permission is, they trust Keith more for asking for it.

Shiro is smiling up at Keith, propped up by his single elbow on the edge of the examination tank, his long tail sloshing gently through the two-foot-deep water in the little enclosure. It’s tiny and cramped compared to his regular tank, with just enough space and water to keep him comfortable while still giving Keith enough access to do his exam. He’s looking into Keith’s eyes but he doesn’t seem to be paying attention.

This time, Keith touches Shiro’s wrist to make his intention clearer. “Can I?” he says.

Shiro’s eyes flick down to where Keith is touching him. With a flash of recognition, he holds out his arm for Keith to attach a blood pressure cuff and waits patiently for it to inflate.

“That’s it,” Keith says, letting the appreciation show in his voice. Not all of his charges are so cooperative. When he’s done taking readings, he gives Shiro his arm back and adds, “Good numbers. Thank you, Shiro.”

Shiro responds by reaching out to touch Keith’s face before combing his fingers through Keith’s hair. He’s still smiling. Keith silently chides himself for the blush that warms his face.

Keith talks to all the cryptids in his care. But Shiro is different.

It’s only been six months since Shiro arrived – an incredibly rare specimen of merfolk from the deep of the Pacific, so rare that almost nothing is known about his species. The injuries he’d come in with have healed down to a few shiny scars and a right arm that ends just below the deltoid. Despite the damage, he’s startlingly beautiful. His remaining arm is strong and shapely, his chest broad and muscular, his abs like a washboard. His face is square-jawed, open and trusting, with warm gray eyes and an easy smile. If he were human, Keith would have been attracted to him.

No, Keith has to admit it: he is attracted to Shiro. And not just for his human features. He’s caught himself admiring the gradient near the bottom of Shiro’s pelvis where his bare skin turns into a sheet of scales so fine they feel silky to the touch. His tail twists and curls behind him, much longer than human legs, and strong enough to propel him through the water like a torpedo. Fins decorate every line and curve of him – supple cartilaginous spines vaned with almost-translucent skin – and seem to react to his mood, plastering down to his body when he’s relaxed and flaring up to make his big frame even bigger when he’s threatened or excited. The ones on the sides of his head, where his ears should be, are the most expressive, and when Keith is around they’re almost always extended and swiveling happily.

Shiro likes Keith.

Back when Keith first started working with Shiro, he was surprised by his intense stare and focused presence. Shiro watched Keith’s every move and responded to his every word with guarded attention. It’s still hard sometimes to remember that Shiro can’t understand what Keith is saying, because the way he considers Keith’s requests, hangs on his explanations, and glows at his praise seems to indicate a deeper intelligence than just a wild animal. Keith has to remind himself daily the dangers of anthropomorphizing. He can’t let his personal fondness for Shiro trick him into reading too much into what are surely natural behaviors. He can’t let his attraction convince him Shiro is more than he is.

Even so, Keith catches himself talking to Shiro more than any of his other charges. Instead of simply narrating his actions in reassuring tones, coaxing, and praising, Keith has entire conversations. They’re one-sided, of course. Even if Shiro were able to understand, he can’t speak. His unique combination of lungs and gills doesn’t allow for a voice box. But in some ways it’s not so one-sided, because Keith doesn’t think he’s imagining it when Shiro listens, rapt, as Keith rambles on about his days and his thoughts and his hopes and dreams. He doesn’t respond in words, but by happy flashes of his fins, by catching Keith’s hand out of the air to squeeze it gently, by swimming close to bump against Keith’s body with his shoulder or the side of his head.

It didn’t take long for everyone at the facility to see that Keith is Shiro’s favorite. Keith couldn’t keep their connection a secret, not with the way Shiro follows him on the other side of the glass when Keith walks by his tank, swimming to match Keith’s speed and grinning while turning loops and flips to show off. So they scheduled Keith more time with Shiro, and their friendship grew. When Keith worried about his other patients, he opened up to Shiro. When he was frustrated with his coworkers, Shiro heard about it. And last month, on the day when everyone wondered why Keith was in such a dark mood, Shiro was the only one who got to hear the reason: it had been the anniversary of Keith’s dad’s death. 

By now, Keith has told Shiro more about himself than he’s told any living human. It’s a pity he doesn’t understand.

Today, Keith quickly moves through Shiro’s routine medical check. Nothing is out of the ordinary, and Shiro knows all the steps by now. He even leans over the edge of the tank and opens his mouth for the thermometer before Keith has a chance to take it out of his exam kit. When Keith is done, he scratches the base of Shiro’s ear-fin fondly. His soft, white hair thins out there and the scales that dot his skin rasp on Keith’s fingertips pleasantly. Shiro closes his eyes and leans in to the touch.

As Shiro’s body relaxes, he rolls closer to Keith and his tail flops over to reveal the lighter-colored scales on his underbelly, the tucked spines of pelvic fins flanking a soft pink opening in his scaled skin. On a fish, it would be a vent. Possibly a cloaca. But so far Shiro’s anatomy hasn’t matched up exactly with humans nor fish, nor any other kind of animal for that matter, and Keith suspects it’s some unique configuration of a recto-genital slit. He hasn’t checked yet, though. As important as his research is, it’s more important to Keith that Shiro never feel threatened by his exams.

His scratching has slowed. Shiro grunts impatiently and mouths Keith’s wrist, asking for more. Keith gives him a few more scratches before smoothing the scales back down behind the fin and patting his hair to get his attention.

“I just need to examine here, if it’s okay.” His hand hovers over the slit, indicating without touching.

Shiro blushes. Keith’s never seen that before. The color starts on the bridge of his nose, highlighting the scar there, before spreading across his cheeks and even onto his ear-fins. For a second Keith fears Shiro will tuck his tail back underwater and their session will be over. But then Shiro arches his back, raising the slit out of the water and offering it to Keith.

Keith is sure to be gentle as he strokes the outer lips, noting how soft and slick they are. The scales end here and give way to silky mucous membrane like the inside of a mouth. Keith glances up to check Shiro’s face, making sure he still looks comfortable despite the deepening blush, before easing his fingers inside.

The rim gives way to pressure, and Keith is surprised at how easily his three fingers dip below the surface. He could probably fit his whole hand in there with little trouble. The slick walls flutter and clench against Keith’s knuckles, and the fins on either side of the slit twitch as they start to fan out.

“Does that hurt?” Keith asks. Shiro isn’t paying attention. His eyes are on Keith’s hand where it sits halfway inside him, and he’s sucked his lower lip between his teeth. He doesn’t look like he’s in pain, but his breathing is a little fast, probably from the stress. Keith decides to be quick in case Shiro won’t tolerate this for much longer.

He identifies anatomical landmarks by feel. At the bottom of the slit is a little round pucker of what must be an anus. Keith slides one finger inside to check. Yes, it’s an anus, and he even finds the smooth dome of a prostate when he pushes his finger in a little deeper. He rolls his finger over it a couple of times, checking it for size and symmetry, before withdrawing. There’s no scrotum in front of the anus, just a slight bulge on the bottom of the slit. When Keith presses on it, he palpates two structures just under the skin that he thinks must be internal testes.

At the top of the slit Keith finds a fleshy mound he can’t quite identify. He scissors his fingers apart, trying to open the slit enough to see inside, but Shiro gasps and clamps down on him before he can get a good look. As Keith swirls his fingers around it, tugging and probing, it pulses once and begins to unfurl. The lips of the slit relax and spread apart to allow what Keith now recognizes as a penis to poke its way into the light.

“Oh, are you excited?” Keith presses on the base of the penis and feels something clench and release under his fingers. With each pulse, it grows longer and thicker until there’s no way it could fit back into the slit it came from. Keith strokes his fingers up and down its length, fascinated by the change. It’s almost the size of an average human penis now, and still growing, its surface so slick Keith wouldn’t even need lube to…

Whoa. No. Now of all times, Keith needs to keep his interest solely scientific. He remembers to glance up at Shiro’s face and finds him looking dreamy with half-lidded eyes, mouth fallen open, breath coming fast and shallow.

“Is this okay?” Keith stammers.

Shiro looks directly into Keith’s eyes and nods his head.

Keith freezes, his fingers still inside Shiro’s body, his hand still cupping his growing erection. This isn’t a trick of his emotions. He’s not over-interpreting some naturally explainable behavior. Not this time. He asked Shiro a question, and Shiro nodded yes.

“Can you…” Keith drops his voice low and leans close so only Shiro can hear. He’s not sure who he’s trying to hide from. They’re they only two in the room. Still, he whispers, “Can you understand what I’m saying?”

It’s not the first time he’s asked, and it’s never before earned him anything more than a blank stare. But this time Shiro looks left and right, brow furrowed and fins drooping with concern. Like he has a secret he’s hesitating to share.

“It’s just us,” Keith assures him, forcing himself to speak louder. Antok went home early today, Thace is working on the other side of the complex, and Kolivan will be in his meeting for at least another hour. “No one’s listening, no one’s coming. Tell me. Do you understand me?”

Shiro stares at him with an unreadable expression for what feels like minutes. His poker face finally breaks with a sigh. He tilts his chin up, then down, so this time the nod is unmistakable.

“Oh my god.” All this time, they’ve been treating Shiro like an animal. They’ve put him in an enclosure, subjected him to tests and research, talked about him to his face as if he couldn’t understand. But he’s a person. “I’m sorry,” Keith breathes, pulling his hand away.

But before he can retreat fully, Shiro grabs his wrist. He opens his mouth, then closes it and twists it into a frown as if frustrated he can’t explain himself. His eyes look up at Keith plaintively as he tugs on his wrist, silently urging Keith to come closer.

“You want me to keep going?” says Keith.

Shiro nods eagerly.

“With the exam?”

This time, Shiro shakes his head no.

“What do you…”

Shiro ends Keith’s questioning by surging out of the water to kiss him. It’s artless but earnest, a gleeful press of tongue against Keith’s lips, as if Shiro has perhaps seen humans kissing but hasn’t had a chance to practice himself. Keith is stunned only for a second before responding in kind. Shiro’s tongue is long and supple; Keith sucks it into his mouth and locks lips with Shiro, teaching him by demonstration how to kiss properly. Shiro is a quick study. It isn’t long before his kisses, and his fist twisted into Keith’s hair, make Keith’s knees go weak.

Keith’s lab coat is on the ground before he realizes that Shiro has started to undress him. Shiro’s hand dives under his shirt, and it’s the shock of the cold and wet on his bare skin that snaps him back to reality. Shiro’s penis has grown to its full size, its firm bulk is pressed between their bodies up against Keith’s midsection. It’s as long as Keith’s forearm and as thick as his wrist, tapered at the end and flaring to a wide base where it protrudes from the scaly slit. It’s beautiful and monstrous. Even though the touch of it makes Keith’s loins strain as his own dick tents his pants, Keith tenses and takes a step away from the pool, his higher brain reminding him that he’s on the verge of doing something he won’t be able to take back.

The moment Keith hesitates, Shiro withdraws. He slips back into the pool, ducking below its edge almost sheepishly. When he peeks back out, his scales glistening and his hair plastered wetly against his brow, he tilts his head and seeks Keith’s eyes. He’s trying to say something, shaping his lips around three words as he gestures open-handed to the bulge under Keith’s pants. It takes a few tries for Keith to realize what he’s asking. “Is this okay?” Keith can even hear the click of the “k” in the back of his throat. He repeats it again and again, willing Keith to understand.

In the moment, Keith is rendered as mute as Shiro. All he can do is nod, softly at first, then more emphatically as he makes up his mind. This is okay. He wants this. God, he’s wanted this for months.

He finishes what Shiro started by yanking his shirt up over his head and dropping it on the floor. Shiro is propped up on the edge of the pool again, his tail lashing excitedly behind him. He seems as fascinated by Keith’s body as Keith has been by his. Keith steps closer as he wrestles with the button on his pants so Shiro can run his hand over Keith’s arms and chest. As Keith’s pants and boxers fall, Shiro’s hand explores lower, grasping at the jut of Keith’s hip and tracing the lines of his thighs. He runs a tentative finger down the length of Keith’s dick, huffing something like a laugh as he discovers how different it is from his own – all of it on the outside, and so much smaller. But the shine of his eyes and the curve of his smile all say for him what he cannot: “Beautiful, beautiful.”

Now Keith’s socks are the last slips of fabric between him and nakedness. He kicks them off and climbs into the pool.

He barely has time to feel the shock of cold water before Shiro’s arm is around him, crushing him to his body for a kiss that warms Keith to the center of his chest. That monstrous cock hasn’t shrunk at all in the cold. It nudges up under Keith, pulsing with each kiss, its length running from under his balls through the cleft of his ass and leaving a slick trail as it goes. Keith rocks his hips to slide it back and forth. Its slippery surface feels delicious on the insides of his thighs and against his hole.

“Lie back,” Keith pants. “I want to taste.”

Shiro, ever obliging, reclines in the water so his cock bobs to the surface. Keith straddles his tail on hands and knees. He doesn’t have a hope of fitting the whole thing in his mouth, but he licks and sucks on the side of the shaft experimentally and enjoys the way the fins bordering the slit twitch and tremble with each touch of his tongue. Shiro tastes like the salt water he moves through and, once that’s licked away, musky and rich and just a little bit fishy.

Keith reaches back and teases his own hole. It’s been aching to be filled since he first saw Shiro’s cock, and now it’s so slippery from rubbing up against Shiro that two fingers slide inside easily. He fingers himself slowly as he stretches his mouth around the head of Shiro’s cock. No more than the tip will fit past the back of his throat no matter how hard he pushes, and the effort only makes him burn and gag, but he feels a thrill of victory at being able to suck on even a quarter of its length. When he glances up through choked tears, Shiro’s chin is on his heaving chest, mouth open in a silent moan, each breath hissing in the back of his throat as if he’s trying despite his anatomy to make a sound.

The sight is so beautiful, a strangled whimper makes it out of Keith’s stuffed mouth as he fucks himself hard with his fingers. Shiro watches, captivated. He splays his hand across Keith’s shoulder blades and smooths it down Keith’s back until his fingertips brush Keith’s wrist where it’s working back and forth. He catches Keith’s eyes again and manages to ask permission with just his eager expression. Keith moves his hand out of the way for Shiro, who immediately takes over with two fingers of his own, plunging them in to the last knuckle in one smooth movement.

Keith’s full mouth is the only thing that turns his surprised yelp into a muffled groan. Shiro’s fingers are much thicker than his own, and the sudden stretch toes the borderline of painful. He almost asks Shiro to stop, almost explains how to open him up gently, but he’s so hungry for it he can’t bring himself to slow Shiro down. He licks the underside of that gorgeous cock and tries to work out how many fingers would equal its thickness. When Shiro works a third finger in beside the first two, his eyes shining as he marvels at the way Keith widens to accept him, Keith takes a deep breath and forces himself to relax.

He doesn’t have attention to spare for sucking cock anymore. His body goes slack and rigid by turns, and all he can do is rake his fingernails down Shiro’s back and whine as Shiro’s fingers coax him wider and wider. Just as the natural lubrication starts to thin, making Keith sting from the friction as well as the stretch, Shiro pulls his fingers out. Keith’s sob of relief becomes a gasp as Shiro grips him by the hair and flips them both over. Keith is on his back in the water, the length of Shiro’s body pressed against him from above. A column of soft scales forces his knees apart and he feels the slick tip of Shiro’s cock stroking him, prodding for its way in.

Keith surrenders. His head drops back into the water; his legs fall open. Shiro is too strong for Keith to resist. Now that he’s set this act in motion, there’s nothing for him to do but give himself over to it. Isn’t this what he wanted? What he fantasized about? To be utterly taken by a monster?

But Shiro doesn’t force his way inside. Instead, that little grunt in the back of his throat makes Keith open his eyes. Shiro is looking down at him with furrowed brow and parted lips. He bumps their noses together with a little huff of concern until Keith stammers, “Sh-Shiro?”

Shiro mouths that word again, the back of his tongue clicking out the only audible letter in the middle of it: “Okay?”

“Yes…” Keith chokes around helpless tears. “Yes, yes, it’s okay, please, Shiro, I want you, please, put it inside me…”

Shiro kisses him as his body surges. Keith feels the tapered tip wedge him open just before every inch of the shaft drives up into him, churning his insides and knocking the wind from him. He’s so full, so impossibly full, ecstasy barely masking the pain of it, and he feels like his belly must be bowing out from the pressure. But the water provides no leverage, and as soon as the first thrust is done Shiro begins to fall away. Inch by inch he slides out, leaving a delicious drag on Keith’s rim and a hungry emptiness in his core.

“Again!” Keith sobs, and when Shiro thrusts into him a second time up to the thick base of his cock, slit bumping against Keith’s rim and spiny fins brushing his cheeks, Keith releases the scream he’s been holding in. It’s too much, too much, but he’d rather die than tell Shiro to stop. His voice cracks raspy and high-pitched as he begs, “More, more, more!”

Without legs, without a floor to brace against, there’s no pattern to Shiro’s thrusts. He whips his tail in the shallow water while pulling Keith against him by his hair, thrashing up into him again and again. The movement tugs Keith’s hole from side to side while the long shaft breaches him. Each thrust is intense enough to make Keith’s vision go funny. Some part of him remembers that what’s happening here should stay a secret, but that part of him can’t overcome the part that’s screaming loud enough to be heard, Keith is sure, in the next wing over.

Keith reaches down between his legs with a shaking hand to touch his rim where it’s stretched tight around Shiro’s thick cock. As it thrusts into him, he blinks away the spots in his vision and gropes along the shaft until he finds the slit – puffy and slick and spread wide around the erection protruding from it. Shiro trembles as Keith strokes it, and his next thrust is weaker, unfocused. This time, Keith’s whole hand fits inside easily.

Shiro mashes his face against Keith’s, too reflexive to be a kiss. His mouth works open and closed involuntarily. Keith twists his hand inside the slit, fucking Shiro even as Shiro fucks him. He finds the puckered hole at the base of the slit and positions his hand so the next time Shiro thrusts into him, he impales himself on two of Keith’s slender fingers.

Shiro’s tail whips erratically, frantically, sloshing water onto the floor in great waves as he fucks Keith with wild desperation. Their kisses devolve to a frenzied press of lips, each panting into the other’s mouth. Keith doesn’t think he’ll be able to come with something so big inside him until an orgasm rises up like a sneaker wave to batter him into the sand. He can’t even scream anymore, can’t even see, as his body flails against Shiro’s with spasms like drowning.

He sucks air as the pleasure fades, his vision clearing as the wave recedes. Shiro is still fucking him, and he’s so sensitive now that it’s unbearable. He’s about to beg for mercy when one last thrust makes Shiro curl against him with a shake that wracks his whole body. Keith feels Shiro’s orgasm as a rising, hot pressure in his gut, and he lets out an exhausted moan as he’s pumped full of his come.

They float there, locked together by handholds and tangled limbs, while they catch their breaths. Keith doesn’t think he’ll ever be able to stop trembling, but when Shiro’s cock finally recedes enough to fall free of his ass and the chilly water soothes the burn on his rim, his legs go boneless and his pleasure-beaten muscles uncoil. He works his fingers free of Shiro’s hole, but keeps his hand inside the slit until he feels that enormous cock dwindle back to a little nub and tuck itself back below the surface.

Keith can’t make his limbs move to swim, so he lets his heels drop to the floor of the shallow pool while the air in his chest buoys him up. Water laps at his forehead and ears but his face bobs just barely above the surface, his arms floating at his sides, his back arched by buoyancy and gravity, too loose to stop the come from trickling out of him. The saline-tart water is so comfortable and inviting, and he’s so dizzy with euphoria, that he lets the air out of his lungs and doesn’t care when his nose and mouth slip underwater.

Shiro’s tail coils under him and lifts him back into the air, his hand on the nape of Keith’s neck holding his head up. Keith answers the unspoken concern on his face, “I’m okay.”

“Okay,” Shiro mouths with a shy smile. They float together, Keith safe in Shiro’s scaly embrace, until the room around them fades out and all that’s left is each other. Keith rests his head against Shiro’s chest and closes his eyes. He can’t hear the ever-present whir of machinery behind the walls of the complex, nor the buzz of the overhead lights. Only Shiro’s heartbeat and the gentle lap of water.


End file.
